1. Field of the Invention
The present invention relates to a display device which displays information, a display panel unit, and an information processing apparatus which processes information and displays the processed information.
2. Description of the Related Art
In the fields of device such as personal computer, there have hitherto been widely used liquid crystal panels being a slim display screen which displays information. Particularly, in laptop personal computers, mobile telephones and the like for which device thickness reduction is especially required, backlight-type display devices in which light is irradiated from the rear face side to the liquid crystal panel have been widely used.
In the backlight-type display device, a light source extending in a linear shape is arranged at the side of a liquid crystal panel, and a light guide plate is attached to the rear face of the liquid crystal panel. Light emitted by the light source is guided to the liquid crystal panel by the light guide plate and further diffused by the light guide plate, so that the light is irradiated from the back of the liquid crystal panel. In such a backlight-type display device, the light source and the drive board which drives the light source are disposed at a flank of the liquid crystal panel which has a relatively large spatial margin, so that the thickness of the display device can be reduced.
Conventionally, in the backlight-type display device, CFL tube (cold cathode fluorescent tube) has been used as the light source. However, the CFL tube uses mercury to emit light. Thus, from a viewpoint of environmental protection, LED (light emitting diode) light source which does not use mercury has been increasingly used instead of the CFL tube. The LED light source has the advantages that it is more desirable in terms of environmental protection and less expensive than the CFL tube. However, the LED light source has problems that heat generation is large with respect to the amount of luminescence, and its life and luminance efficiency are significantly reduced by heat.
In this regard, in the backlight-type display device, the following measures have been taken: a radiator fin which dissipates the heat generated by the LED light source is provided (for example, refer to Japanese Patent Laid-Open No. 2006-267936); a radiator plate for dissipating heat is attached to the LED light source (for example, refer to Japanese Patent Laid-Open Nos. 2006-268066 and 2005-135862); a heat transmission plate which receives the heat generated by the LED light source and transmits the heat to the housing and radiator plate is provided (for example, Japanese Patent Laid-Open No. 2006-293182). When these techniques are applied, the temperature rise within the display device caused by the heat generated by the LED light source can be suppressed to reduce the degradation of LED light source.
In the backlight-type display device using an LED light source, typically, plural LEDs are arranged linearly along the side surface of the liquid crystal panel. However, heat flows in a different manner in each LED depending on the location of placement, thereby making ambient temperatures of the plural LEDs non-uniform. Accordingly, even when the techniques of the above described patent documents are applied to dissipate the heat generated by the plural LEDs, the degree of degradation is not uniform in the plural LEDs and thus the luminosity of display screen in the liquid crystal panel is very unlikely to be uniform.
This problem occurs not only in the display device using a liquid crystal panel but also in the backlight-type display device in general.